Simufact for Fastener industry

Cold Forged Fastener Development utilizing Simufact.forming Software
Nathan Crowgey, Vico Products Co., Plymouth, MI, USA
Abstract
This paper considers the process the Vico Products engineering team contemplated during the
development of a fastener in a six station cold forging machine. The fastener being developed is
double flanged and double threaded with a formed knurl using 10B21 material. Due to these
features, this part poses many challenges in the forming process. This paper will describe the
stations in the part progression that required improvement and how the Simufact.forming
simulation software aided in the development process.
1. Initial Design and Simulation
The baseline tooling design was created using prior successful designs of similar parts Vico
Products has developed. With this fastener being very similar in function, length and diameter, it
was determined that it could be formed with the same basic progression. This initial progression
began by extruding down to the shank diameter
from an intermediate wire size on both the die
and punch sides in the first station. Extrusion of
the thread blanks and the forming of the upset
for the large flange occurred in the second and
third stations while working on the upset for the
large flange. The fourth station then finished
the large flange and knurl blank to complete the
upset forming sequence. Finishing the
progression, the fifth station forms the knurl
while the sixth station forms the small flange.
This basic progression is shown in Figure 2. As
Figure 1: Fastener in Development
C-O St1 St2 St3 St4 St5 St6
Figure 2: Initial Design Progression
described, this tooling design contained three stations for working on forming the flange and knurl
blank before having to extrude the knurl. In previous designs, this concept proved to produce knurl

lanks that extrude full and sharp knurl teeth. The progression was then finished with an open die
upset of the smaller flange in the sixth station. This initial design progression was simulated using
Simufact.forming. The results of the first station simulation showed that simultaneously extruding
on the die and punch sides per the initial design produced immediate buckling. This information
proved useful in allowing the design team to make the necessary modifications to the tooling
design prior to tooling fabrication. Simulation of the following stations was not completed due to
failure of the fastener in the first station. It was concluded that this failure in the first station was
due to the combined load created by open extruding, near the recommended limit, on the die and
Figure 3: 1 st
Station Buckling
punch sides simultaneously, which exceeded the column strength of the steel.
This resulted in the uncontained portion of the shank buckling. This simulation
result is shown in Figure 3.
2. Redesign of First Station and Simulation
The buckling effect produced from the initial design required extrusions on the
die and punch sides in the first station to be separated into two stations. In the
second design, initial extrusion on the die side was in the first station and the
initial extrusion on the punch side in the second station. This was not a desired
situation because it reduced the number of stations available for forming the
large flange and knurl blank. To accommodate this extrusion in the second
station, one of the upset forming stations had to be eliminated. The third
station upset in the initial design was the
station that was removed as a part of the
second design. The upset in the second
station in the initial design was then modified
by having the gap between the die and
punch reduced to make the upset form
Figure 5: 4 th Design
Underfilled Blank
closer
in
shape
to the
C-O St1 St2 St3 St4 St5 St6
Figure 4: 2nd Design Progression
initial third station part. This re-design places much more
importance on getting optimum material flow out of this
second design third station. The fourth station remained the
same since the part going into the fifth die needs to be the
same regardless of the other upset forming changes. The
re-designed progression is in Figure 4. The results from running
the second design through Simufact.forming simulation showed

that the extrusions in the first and second stations formed without any buckling with these design
modifications. Upsetting in the third station formed as predicted however, the material did not flow
as planned in the fourth station. The knurl blank did not fully fill out to the dimensional requirements
and therefore during simulation of the fifth station, it produced an under filled knurl profile. The
under-filled knurl blank simulation result is shown in Figure 5. The simulation of material flow of
the third station part into the flange cavity in the fourth station also showed that there was a lack of
material in that upset shape, shown in Figure 6. In that
simulation, the material also pulled away from the
undercut feature as it was flowing out into the flange
cavity leaving a void between the die and the material. It
was concluded that the third station upset form would
require modification to provide more material to fill out the
flange cavity as well as a revised shape to aid in filling out
the knurl blank. Due to time constraints, tooling had to be
ordered and this second design had to be sampled in the
machine. The results were consistent with those produced with
the Simufact.forming software. Some minor modifications were
made to the tooling during the sample run but those changes did
not make enough of a difference to produce a quality part.
3. Redesign of Upsets
The concept in redesigning the upset stations was to work on the
volumes, angles and lengths of the die and punch shapes so that the
material would flow easily into the flange cavity in the fourth station and
thus fill out the knurl and flange in the fifth station. Simufact.forming
provided a lot of information to aid in determining how to go about
modifying the third upset. In analyzing the initial and second designs, the
simulation animations illustrated where the material voids occurred and
thus showed where the material needed to be in the third station to
produce the desired results in the fourth station. Using this information, it
was concluded that in station 3, the punch side lead angle on the face
needed to be steeper and the shoulder needed to be lengthened. It was
also determined that on the die side the face angle had to be opened up
and pushed deeper. The sum of these changes were intended to aid in
guiding the material outward in a more controlled manner as well as drive
Figure 6: 4 th Station
Under-filled Flange
Figure 7: 3rd
Design Tooling
material down into the knurl shoulder. The third station tool concept is shown in Figure 7. These
modifications did improve the results in simulation and the fourth station did fill out better however,

it was felt that more changes could be made at this stage to produce better results before
attempting another machine run.
After reviewing this third design and the Simufact.forming results, it was determined by the
engineering team that the next design to be simulated would follow a different concept. This
iteration varied by having a counter bore at the face on the punch side instead of an angle leading
into the counter bore as was the case in the previous design. This third punch design is shown in
Figure 8. In this fourth design, the assumption was that the material would first fill into the counter
bore and then upset into the gap between the die and punch. The results of this situation were
good in simulation. The first and second stations remained unchanged from the previous two
designs. In the third station the material filled into the counter bore and upset between the die and
punch sides. In the fourth station, the part formed in the third station filled into the knurl shoulder
and into the flange cavity providing a fully filled out fourth station
part. The part formed in the fourth station was simulated in the fifth
station as well and the resulting part displayed a fully filled out knurl
profile. With this outcome the fourth design was tooled up and set
up in the machine. However, the actual results from manufacturing
run did not match the simulation results. The engineering team
concluded that this was because in the third station of the sample
run, the material did not fill into the counter bore fully as was displayed in simulation which resulted
in a lack of material in the fourth station to fill the knurl blank. This under- filled counter bore in the
third station was due to oil and material coating residue being trapped into the corner of the punch
counter bore preventing the material from flowing all the way in. Due to this condition the third
station counter bore on this header run was actually more under filled than with the previous
design.
On the fifth and final design, a steep angle was placed at the face of the third station punch going
back to the thread blank with no intermediate counter bore. This punch design is shown in Figure
9. Initially this did not seem like it would provide the best results in
material flow and filling out the corners and cavities in the fourth
station but it was ran through Simufact.forming and displayed the
best balance of filling out the knurl blank as well as fully filling out
the flange form without excessive flashing in between the die and
punch. This design was run in the last header trial and provided
improved results. The parts produced in third and fourth stations
Figure 8: 4th
Design Punch
Figure 9: 5th Design Punch
were then able to continue on to the last two stations. Being able to run through several iterations
using simulation in a relatively short period of time was very beneficial in developing a successful
progression and being able to simulate ideas and designs that may otherwise have been passed
over or ruled out because of the time and cost in manufacturing each iteration in the header. Once

passing through the upsetting stations with the desired blank, the knurl and open die stations
worked with little adjustment or modification.
4. Knurl and Open Die Stages
While the primary struggles experienced on this part were in manipulating the upset forms, the fifth
and sixth stations still benefited from simulating their forming processes. The knurl extrusion on
the initial design of the fifth station did not form the knurls as fully and
cleanly as anticipated even though the entering blank was filled. It
was initially assumed that the diameter of the knurl blank needed to
be increased however it could not be proven. While this job was still
in the machine, the engineering team was able to set up another
Figure 11: 5 th Station Filled Knurl
simulation trial to attempt to
replicate the situation in the fifth
station, to see what was causing
the under-filled condition. The
animation of that simulation
showed increasing strain at the
start of the knurl extrude as the part
pushed into the punch and also showed the knurl starting to
under fill as seen at the machine. The under-filled fifth station
simulation is shown in Figure 10. With this information,
another simulation was set up with a modification to the lead-
in angle and radius of the knurl extrude in an attempt to reduce that resistance and the knurl filled
out fully. The results of that simulation produced a full, sharp knurl that formed with less
resistance. The simulated full knurl is shown in Figure 11. This verified that the knurl blank was
correct and that it was the knurl extrude that needed to be modified. At the machine, the fifth
punch knurl extrude was modified according to the simulated fifth punch and the knurl filled very
similarly to the simulation animation.
In the sixth station, using the results from the newly re-designed fifth
station simulation, the first simulation was evaluated and it produced
a finished part very close to design specifications with no
modifications, shown in Figure 12. Analyzing the simulation results, it
was determined that the design of the tooling for this station was
acceptable however some minor adjustments needed to be made at
the machine to get the finish part fully to the print specifications.
Making these small changes did bring the part into the print
specification and Vico Products was then able to finish the rest of the
processing of this part to submit a sample to the customer.
Figure 10: 5 th Station
Under filled Knurl
Figure 12: 6 th Station
Filled Out Open Die

5. Conclusion
The application of the Simufact.forming Simulation software provided invaluable information at a
critical time in the design process. It afforded the opportunity to see how the initial design formed
and allowed multiple iterations to be made to the design prior to purchasing any tooling. In
addition after each machine run, the simulation software was able to provide valuable insight into
what was actually going on with the material flow so further development and re-design could head
in the most practical and efficient direction. The progress attained from simulation in the refining of
the upset forming on this part allowed for fewer machine runs as well as providing more confidence
in the design and manufacturing results. Past development of similar parts took a great deal more
time and resources to achieve the same result.